Utility skid tree support system for subsea wellhead

ABSTRACT

A utility skid tree system for subsea wellheads enables a tree to be mounted by and interface with utility skids. Production bore access is provided through an extended production wing block. The system reacts and transfers installation loads and potential snag loads to the conductor. The tree accepts skids for flow boosting, metering, water-oil separation, etc. A conventional choke may be fitted outboard of the utility insert profile.

This patent application is a continuation-in-part (CIP) of U.S. patentapplication Ser. No. 11/595,444, filed Nov. 9, 2006, having AttorneyDocket No. V2003047A, and entitled Tree Mounted Well Flow InterfaceDevice.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates in general to subsea wellheads and, inparticular, to an improved system, method, and apparatus for a utilityskid tree support system for subsea wellheads.

2. Description of the Related Art

In one type of offshore well production, a subsea production tree isinstalled at the sea floor. The tree may be connected by a flowlinejumper to a subsea manifold, which may be connected to other subseatrees in the vicinity. A production riser may extend from the subseamanifold or from an individual tree to a processing facility, normally afloating platform. The well formation pressure is normally sufficient tocause the well fluid to flow up the well to the tree, and from the treeto the processing facility.

In very deep water, the well may have sufficient pressure to cause thewell fluid to flow to the tree but not enough to flow from the sea floorto the processing facility. In other cases, the well may even lacksufficient pressure to flow well fluid to the sea floor. Downholeelectrical submersible pumps have been used for many years in surfacewells, but because of periodic required maintenance, are not normallyemployed downhole in a subsea well.

A variety of proposals have been made for booster pumps to be installedat the sea floor to boost the well fluid pressure. However, because ofthe pump size, installation expense and technical difficulties, suchinstallations are rare. When such configurations are used, large utilityskids are typically used to move equipment to and from the subsea wellfrom the surface. Utility skids are cumbersome and manipulating themwith respect to the well can be very difficult if not hazardous tooperators and the well installation itself. Thus, an improved system andmethod of facilitating interaction between subsea wells and utilityskids would be desirable.

SUMMARY OF THE INVENTION

Embodiments of a system, method, and apparatus for a utility skid treesupport system for subsea wellheads are disclosed. The invention enablesa tree to be mounted by and precisely interface with utility skids.Production bore access is provided through an extended production wingblock. The system reacts and transfers installation loads and potentialsnag loads to the conductor. The tree accepts skids for flow boosting,metering, water-oil separation, etc. A conventional choke may be fittedoutboard (i.e., downstream) from the utility insert profile.

The foregoing and other objects and advantages of the present inventionwill be apparent to those skilled in the art, in view of the followingdetailed description of the present invention, taken in conjunction withthe appended claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features and advantages of the presentinvention, which will become apparent, are attained and can beunderstood in more detail, more particular description of the inventionbriefly summarized above may be had by reference to the embodimentsthereof that are illustrated in the appended drawings which form a partof this specification. It is to be noted, however, that the drawingsillustrate only some embodiments of the invention and therefore are notto be considered limiting of its scope as the invention may admit toother equally effective embodiments.

FIG. 1 is a sectional side view of one embodiment of utility skid treesystem constructed in accordance with the invention;

FIG. 2 is an isometric view of a subassembly of the system of FIG. 1 andis constructed in accordance with the invention; and

FIG. 3 is an isometric view of another subassembly of the system of FIG.1 and is constructed in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1-3, embodiments of a system, method and apparatusfor a utility skid tree support system for subsea wellheads are shown. Awellhead housing 11 is located at the upper end of a subsea well.Wellhead housing 11 is a large tubular member mounted to a conductorpipe that extends to a first depth in the well.

A subsea Christmas or production tree 13, such as a horizontal or spooltree, is secured to the upper end of wellhead housing 11 by aconventional connector. Tree 13 has a bore 15 that contains a tubinghanger 17. Tubing hanger 17 supports a string of tubing 19 that extendsinto the well for the flow of production fluid. Tubing 19 registers witha production passage 21 that extends through tubing hanger 17. A lateralproduction port 23 extends from production passage 21 through aproduction master valve 25 within tree 13.

Production passage 21 of tubing hanger 17 has a crown plug profile 31located above lateral production port 23. Profile 31 is adapted toreceive a plug normally lowered and retrieved by a wireline. Tree 13 hasa mandrel 33 on its upper end containing an external grooved profile. Anadapter 35 lands on tree 13. Adapter 35 has a conventional,hydraulically-actuated connector 37 for connecting to tree mandrel 33.Adapter 35 has a seal sub 39 that extends downward into sealingengagement with production passage 21 in tubing hanger 17. Adapter 35has a production passage 41 that registers with seal sub 39 for the flowof production fluid. An isolation valve 43 and a retrievable plug 45 arelocated within production bore 41. A swab valve may be used in lieu ofplug 45.

A lateral production port 47 extends from production bore 41 betweenvalve 43 and plug 45. Adapter 35 preferably has a mandrel 49 on itsupper end that receives a debris cap 51. Lateral production port 47connects to an intake conduit 53. A flow interface device 55, such as asubsea pressure intensifier or oil separator, is connected to intakeconduit 53, which is preferably shorter than it appears in the drawings.

The device 55, or an outlet conduit extending therefrom (not shown), isconnected to a utility skid tree support system 61. In one embodiment,system 61 comprises a wing block 63 having an extended length, ahorizontal bore 65 and a vertical bore 71 extending upward therefrom todevice 55. The wing block 63 may be mounted to tree 13 as shown on a lip66, or integrally formed with tree 13 (not shown). Horizontal bore 65has a production wing valve 67 that is mounted adjacent to and in fluidcommunication with production master valve 25 and lateral productionport 23. Horizontal bore 65 may be interconnected to a choke body 69,which also may comprise a T-conduit or still other equipment.

As best shown in FIG. 1, production wing valve 67 may be locatedhorizontally closer to production master valve 25 than to an end face 70of wing block 63. In contrast, vertical bore 71 is located horizontallycloser to end face 70 than production master valve 25. In a similarnon-symmetrical sense, horizontal bore 65 is located closer to left sideface 72 (FIGS. 2 and 3) of wing block 63 than right side face 74thereof.

In one embodiment, a block leg 73 extends downward from wing block 63directly beneath wing valve 67. Block leg 73 extends across the entirewidth W of wing block 63, and has a horizontal lower surface 75 and achamfer 77 as shown. In addition, a wide groove 79 is formed on a topsurface 81 of wing block 63. As shown in FIG. 2, groove 79 may extendfrom end face 70 to tree 13 as shown. Alternatively, groove 79 may beoffset from end face 70 (FIG. 3) and intersect an orthogonal shelf 83formed below and parallel to top surface 81. In one embodiment, groove79 is located directly above horizontal bore 65, such that it too iscloser to left side face 72 than right side face 74. This configurationsegments the top surface 81 into a smaller portion (see left side ofFIG. 2) and a larger portion (right side of FIG. 2). A complementaryvertical groove 85 is formed on the side of tree 13 and aligns withgroove 79.

Referring again to FIGS. 1 and 3, the support system 61 furthercomprises a utility skid 101 having an elongated body with a rectangularfoot 103 extending downward therefrom. Foot 103 is closely received bygroove 79 (FIG. 3) and groove 85 (FIG. 2) in tree 13 for matingengagement therewith. A flat ring 105 protrudes horizontally from a treeside end of skid 101. Ring 105 has an opening 107 for receiving mandrel33 as shown, which helps to locate and align skid 101 with respect tothe tree 13 and support system 61. Skid 101 may be provided with anoptional tab 109 that extends vertically downward from an opposite endthereof with respect to ring 107. Tab 109 engages vertical bore 71 inwing block 63 to complete a mating alignment between skid 101 and wingblock 63.

In operation, the well would initially be producing with sufficientpressure to flow well fluid to a surface processing facility. In suchcase, adapter 35, device 55 and its conduit 53 would not be locatedsubsea. Instead, a choke insert (not shown) may be located in choke body69. An internal tree cap (not shown) would be located at the upper endof tree 13 for sealing bore 15. A plug (not shown) would be located inprofile 31. The fluid would flow out through valves 25 and 67, throughthe choke in choke body 69, and into a production flow line.

If the pressure of the well depletes sufficiently so as to require abooster pump, the operator would then connect a riser (not shown) totree mandrel 33. The operator closes valves 25, 67, which along withproduction port 23, make up a main flow path. The operator removes theinternal tree cap through the riser while leaving the crown plug withincrown profile 31. With the assistance of an ROV, the operator removesthe choke insert from choke body 69. The operator then removes the riserand lowers adapter 35, device 55 and its conduit 53 as a unit. Seal sub39 stabs sealingly into tubing hanger bore 21. Connector 37 connectsadapter 35 in place, and device 55 is connected to wing block 63. Adownward force due to the weight of device 55 passes through adapter 35and tree 13 into wellhead housing 11.

The operator reconnects the riser at this time to adapter mandrel 49.With a wireline tool, the operator removes plug 45 from its positionabove lateral production port 47. The operator opens valve 43 andremoves the crown plug from profile 31 and reinstalls plug 45 aboveproduction port 47. Alternatively, the crown plug could be re-locatedfrom profile 31 to the position above production lateral port 47, thusserving as plug 45. The riser is removed and debris cap 51 is installedon adapter 35.

Opening valve 97 and supplying power to pressure intensifier 109 causeswell fluid to be flow from production bore 76 through passage 96, port101, and conduit 107 to pressure intensifier 109. Pressure intensifier109 pumps the fluid out conduit 111 through choke body 83 into the flowline. Adapter passage 96, conduits 107, 111 and pressure intensifier 109thus create a bypass flow path.

Device 55 also may operate in combination with a downhole electricalsubmersible pump suspended on tubing. If the assembly is to be used asan injection well, device 55 would operate in the reverse direction andfluid would flow from choke body 69 to device 55, which pumps fluid downproduction passage 21. If device 55 is to be utilized from thebeginning, it could be lowered and installed initially along with tree13. In that instance, a T-conduit would typically be used for choke body69. For removing device 55 to repair or replace it, the operatorattaches a riser, removes plug 45 and lowers a crown plug into crownplug profile 31.

Alternately, plug 45 may be released, lowered and reset in crown plugprofile 31. The operator disengages connector device 55 and connector 37and retrieves the assembly to the surface. The operator then lowers theassembly with a new or repaired device 55 and repeats the process. Inaddition, the operator has the ability of lowering tools or instrumentson wireline or coiled tubing into tubing 19 by removing debris cap 51and connecting a riser to mandrel 49. Plug 45 is then removed throughthe riser, providing access for wireline tools.

The invention has significant advantages. Supporting utility skids witha wing block for the tree utilizes the extensive strength of the treemandrel to avoid the need for specially constructed supporting frames.Equipment such as pump assemblies can be readily installed and retrievedfor maintenance. The assembly allows access to the tree tubing andtubing annulus for workover operations. The system reacts and transfersinstallation loads and potential snag loads to the conductor. The treeaccepts skids for flow boosting, metering, water-oil separation, etc.

While the invention has been shown or described in only some of itsforms, it should be apparent to those skilled in the art that it is notso limited, but is susceptible to various changes without departing fromthe scope of the invention.

1. A production tree, comprising: a tree body having a bore, a lateralproduction port extending from the bore, and a mandrel; a utility skidtree support system having a wing block and a utility skid; the wingblock is mounted to the tree body below the mandrel and has a horizontalbore aligned with the lateral production port, and a vertical boreextending from the horizontal bore, a groove formed on a top surface ofthe wing block; and the utility skid having a foot received by thegroove, and an aligning member for engaging the mandrel to locate andalign the utility skid with respect to the tree body.
 2. A productiontree according to claim 1, wherein the aligning member comprises a flatring that protrudes horizontally from the utility skid and circumscribesthe mandrel.
 3. A production tree according to claim 1, wherein a tabextends vertically downward from the utility skid opposite the aligningmember and engages the vertical bore in the wing block.
 4. A productiontree according to claim 1, wherein the tree body has a lip forsupporting the wing block.
 5. A production tree according to claim 1,wherein the wing block is integrally formed with the tree body.
 6. Aproduction tree according to claim 1, wherein the wing block has aproduction wing valve that is located horizontally closer to the treebody than to an opposite end face of the wing block, the vertical boreis located horizontally closer to the opposite end face than to the treebody, and the horizontal bore is located closer to one side face of thewing block than an opposite side face thereof.
 7. A production treeaccording to claim 1, wherein the wing block has a block leg extendingdownward therefrom, the block leg extending across an entire width ofthe wing block transverse to a direction of the horizontal bore, and theblock leg having a horizontal lower surface and a chamfer on one sidethereof.
 8. A production tree according to claim 1, wherein the grooveextends from an end face of the wing block to the tree body.
 9. Aproduction tree according to claim 1, wherein the groove is offset froman end face of the wing block and intersects a shelf formed below andparallel to a top surface of the wing block.
 10. A production treeaccording to claim 9, wherein the groove is located directly above thehorizontal bore, such that the groove is closer to one side face of thewing block than an opposite side face thereof, and the tree body has acomplementary vertical groove formed on a side thereof that aligns withthe groove.
 11. A production tree, comprising: a tree body having abore, a lateral production port extending from the bore, and a mandrel;a utility skid tree support system having a wing block and a utilityskid; the wing block is mounted to the tree body below the mandrel andhas a horizontal bore aligned with the lateral production port, and avertical bore extending from the horizontal bore, a groove formed on atop surface of the wing block; the utility skid having a foot receivedby the groove, and an aligning member for engaging the mandrel to locateand align the utility skid with respect to the tree body; and the wingblock has a production wing valve that is located horizontally closer tothe tree body than to an opposite end face of the wing block, and thevertical bore is located horizontally closer to the opposite end facethan to the tree body.
 12. A production tree according to claim 11,wherein the aligning member comprises a flat ring that protrudeshorizontally from the utility skid and circumscribes the mandrel.
 13. Aproduction tree according to claim 11, wherein a tab extends verticallydownward from the utility skid opposite the aligning member and engagesthe vertical bore in the wing block.
 14. A production tree according toclaim 11, wherein the tree body has a lip for supporting the wing block.15. A production tree according to claim 11, wherein the wing block isintegrally formed with the tree body.
 16. A production tree according toclaim 11, wherein the horizontal bore is located closer to one side faceof the wing block than an opposite side face thereof.
 17. A productiontree according to claim 11, wherein the wing block has a block legextending downward therefrom, the block leg extending across an entirewidth of the wing block transverse to a direction of the horizontalbore, and the block leg has a horizontal lower surface and a chamfer onone side thereof.
 18. A production tree according to claim 11, whereinthe groove extends from an end face of the wing block to the tree body.19. A production tree according to claim 11, wherein the groove isoffset from an end face of the wing block and intersects a shelf formedbelow and parallel to a top surface of the wing block, the groove islocated directly above the horizontal bore, such that the groove iscloser to one side face of the wing block than an opposite side facethereof, and the tree body has a complementary vertical groove formed ona side thereof that aligns with the groove.